In recent years, larger-sized, higher image quality, and lower power consumption flat panel displays have been required, and high image quality organic EL displays capable of being driven at a low voltage have received considerable attention. The organic EL displays have the following structure. For example, in full color active matrix organic EL displays, thin film-like organic EL elements are provided on a substrate having thin film transistors (TFTs) thereon. In the organic EL element, organic EL layers including red (R), green (G), and blue (B) light-emitting layers are stacked between a pair of electrodes, and each light-emitting layer emits light in response to a voltage applied between the electrodes. This light is used to display an image.
In manufacture of such organic EL displays, thin films such as light-emitting layers and electrodes are patterned by using a technique such as a vacuum deposition method, an ink jet method, or a laser transfer method. For example, in low molecular organic EL displays (organic light-emitting diodes (OLED)), the vacuum deposition method is mainly used to pattern the light-emitting layers.
In the vacuum deposition method, a mask having a predetermined opening patterned therethrough is normally fixed to a substrate in close contact therewith, and is placed in a vacuum chamber so that the mask side of the substrate faces a deposition source. Then, a film-forming material is deposited from the deposition source to a desired position on the substrate through the opening of the mask. A thin film such as the light-emitting layers is patterned in this manner. The light-emitting layer of each color is separately deposited color by color (separate deposition). In particular, a mass production process uses a mask (a full contact shadow mask) having the same size as the substrate, and the substrate having the mask in close contact therewith is typically fixed at a predetermined position with respect to the deposition source when performing deposition.
A vacuum deposition method is also known in which deposition is performed while relatively moving a substrate etc. with respect to a deposition source (Patent Document 1). In Patent Document 1, a mask is used in which a plurality of small holes or long slit holes having a smaller area than an electrode to be formed are formed at predetermined intervals. Deposition is performed while moving the mask in a direction crossing the direction in which the small holes etc. are arranged, whereby the electrode having a predetermined pattern is formed.
Regarding the present invention, a technique is disclosed in which spreading of an scattered evaporation material is reduced by desirably designing the hole shape of an evaporation source (a deposition source) (Patent Document 2). In Patent Document 2, holes through which the evaporation material is emitted toward a substrate have a circular shape as viewed from above, and have a tapered cross section so that the diameter increases toward the outlet of the hole. This allows the film-thickness distribution of the evaporation material to be concentrated in the regions immediately above the holes, and allows the material to be efficiently deposited on the substrate.